U.S. Pat. No. 3,565,691 issued on Feb. 23, 1971 for a "High Energy Density Silver Oxide-Hydrogen Battery" shows a battery formed of electrochemical cells which generate hydrogen upon charging thereof. This hydrogen is stored within the battery container for use during discharge of the battery. Basically each cell of this battery consists of a silver cathode which is oxidized during charging, a gas generating and consuming anode which generates hydrogen during charging, and a separator and electrolyte storage material between the anode and the cathode which stores an aqueous electrolyte for each cell. The hydrogen generated during charging of each cell is stored in an open volume of the battery. The gas pressure of the open volume of the battery is an indication of the total charge of the battery. When the battery is discharged, hydrogen is consumed at the anode of the cell and the silver oxide cathode of each cell is reconverted to silver. During the discharge cycle the pressure of the open gas storage volume of the battery decreases. The battery may be alternatively charged and discharged over its period of useful life.
One application for use of such a silver hydrogen battery is in a space vehicle. In space applications, however, the battery is not subjected to normal gravitational forces. Under such conditions, electrolyte (i.e., water) contained in the separator and electrolyte storage material positioned between the electrodes of each battery cell can vaporize into the gas storage volume. This vaporized material generally condenses on the container walls defining the storage volume. Once the material is condensed on these walls, it is of course lost for future use as an electrolyte. The loss of electrolyte from the system reduces the total amount of hydrogen generating material available and thereby reduces the level to which the battery may be charged on a charging cycle. This action, in turn, reduces the total amount of energy which may be withdrawn from the battery during a discharge thereof.
It is an object of this invention to provide an improved rechargeable electrochemical cell for a battery which eliminates the reduction of battery capacity because of electrolyte loss.
It is another object of this invention to provide an improved rechargeable electrochemical cell for a battery which employs simple, but reliable, structure for reducing the loss of battery capacity because of electrolyte loss.